The present invention relates generally to a mounting formation for metal boxes and a method of forming the mounting formation. The present invention is also directed to a method of mounting electrical outlet boxes to a support structure.
Electrical outlet boxes are well known devices. Illustrative examples showing the general characteristics of electrical outlet boxes are included in the following United States patents:
U.S. Pat. No. 2,757,817 to Egan: Aug. 7, 1956
U.S. Pat. No. 5,703,327 to Jorgensen: Dec. 30, 1997
U.S. Pat. No. 5,603,424 to Bordwell et al.: Feb. 18, 1997
U.S. Pat. No. 5,579,939 to Bourassa: Dec. 3, 1996
U.S. Pat. No. 4,842,156 to Nattel: Jun. 27, 1989
U.S. Pat. No. 5,744,753 to Nattel: Apr. 28, 1998
In new construction, the electrical outlet boxes are typically mounted to wall studs prior to placement of the wall on the studs. Conventional fasteners such as nails and screws can be used in these situations to mount the electrical outlet boxes to the wall studs. Generally the electrical outlet box is configured to accommodate the fasteners at a plurality of locations on at least one side plate to suit the installers needs in the field. Where the electrical outlet box is configured to accommodate fasteners at both side plates, the boxes are usually provided with small holes or larger openings that are fitted with a knock out for at least one of the side plates as required by many national electrical codes. This requirement is generally intended to prevent a rod having a diameter as specified by the electrical codes from being inserted through both side plates. The knock out for this application is generally a substantially circular portion of the wall of the electrical box that is configured to be punched out or bent back in the field by the installer prior to the installation of the fastener. Where holes are provided, the maximum size of the hole is generally limited by national electrical codes which specify the diameter for the rod which cannot be inserted through both walls. In the United States, the Underwriters Laboratories (UL) code currently indicates that the rod diameter is 0.120 inch (3.05 mm). Similarly in Canada, the Canadian Standards Association (CSA) indicates that the rod diameter is 3.0 mm (0.118 inch).
In boxes that are configured to have openings larger than the permissible maximum of about 0.118 inch on both side plates, manufacturers are required to fit the opening with a knockout to ensure compliance with the electrical code. In order to install these boxes in the field, the installers must first punch out the knock out before installing the appropriate fastener. Accordingly, it would be desirable to provide an electrical outlet box having walls configured to accommodate large diameter fasteners without the need to separately remove knock outs prior to the installation of the fasteners.
In accordance with one form of the present invention, a mounting formation for an electrical outlet box having a side plate includes a dome and a flap. The dome has a base and is formed with an opening defined by an edge. The base is connected to the side plate of the electrical outlet box. The flap is connected to the dome and is defined by a perimeter to cover a first portion of the opening while defining a second portion that is uncovered. Preferably the perimeter of the flap and the edge of the opening define a gap having a width less than about 0.120 inch.
In a preferred embodiment of the invention, the base of the dome is preferably configured to be substantially U-shaped having a curved portion and a substantially straight portion. The dome preferably includes a first arch-shaped portion and a second arch-shaped portion. The first arch-shaped portion includes the straight portion of the base and the second arch-shaped portion is connected between the curved portion of the base and the first arch-shaped portion. Preferably the first arch-shaped portion is substantially flat. Preferably the opening is located within the first arch-shaped portion to either partially extend through the straight portion or be adjacent to the straight portion. The opening is preferably positioned substantially in the middle of the straight portion. Preferably the second arch-shaped portion is configured to support the first arch-shaped portion so that the first arch-shaped portion is at an obtuse angle with respect to the side plate. Preferably the flap has a substantially circular shape and the opening has a substantially elliptical shape. The flap is preferably integrally connected to the edge of the opening. Preferably the second portion of the opening is crescent shaped.
These and other objects, features and advantages of the present invention will become apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings.